I know where my '68 Cooper S is, but I was pleased to find that not only is Hector the Mayfair still registered but so is Rosie, my 1100 special which encountered a telegraph pole and caught fire when the engine fell out And so is my '65 MGB, somewhere
Huey & Hector were both first registered in Oxford, Rosie in Swindon & the rest, scrapped or not, in Glos.

My '88 Designer was First Registered 26th August 1988 (exactly 29 years after 621 AOK) ;)First registered in South East London! Now resides in Arlesey in Bedfordshire!Does anyone know where 'HMX' is from exactly?

it says MX is from London North East

In 1988 MX was a South East London plate.

This is a great page for explaining the history of and issuing of plates in the UK.